I think I know the answer to this but I cannot find a definitive answer yet.

Can you equip multiples of the same console?

Example, If you have a console to boost energy weapons by 25%, can you equip a second to get a 50% increase?

Yes, you can stack multiple consoles. And in general they don't stack quite the way you think. Most consoles are just bonuses to an appropriate captain skill such as most science tactical consoles. And some are just bonuses to an an effect of an abilities (i.e. engineering armor consoles and powers that boost hull damage resistance).

Cryptic generally uses a Z x ( 1 + <bonus total> / 100 ) or Z / ( 1 + <bonus total> / 100) type formula for most of their stats. Some stats have more complicated forumlas which have an upper limit on how much you could ultimately get. For instance, damage resistance. You always get more damage resistance by adding armor points. But diminishing returns gets bigger and bigger the high you pile on the armor.

Generally you don't have to worry about diminishing too much until you get to insanely high bonus level a player normally could not reach alone, (i.e. 5 armor consoles, Auxiliary to SIF III, Hazard Emitters III and the same applied from your entire team at the same time.). So get the consoles you feel you need w/o worry.

certain consoles do not stack though, mainly those that are in a set, since they of course are unique. also the consoles off of any of the c-store ships can only have one of a console equipped... no multiple PDS's.